[Bug libstdc++/125514] [16/17 Regression] libstdc++: reference_wrapper triggers -Wsfinae-incomplete for forward-declared type in C++17

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125514

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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   Target Milestone|---                         |16.2
           Keywords|                            |diagnostic